It’s understandable to breathe a sigh of relief after getting a false-positive on a mammogram—meaning receiving an abnormal result that, after further testing such as a biopsy, no cancer is found. But a new study shows that getting a false-positive test result may not mean you’re in the clear.
In fact, the research indicates that women with false-positive mammograms may have a higher risk of developing breast cancer in the future compared to those who tested negative from the beginning.
“This risk may be because of misclassification of a suspicious pattern in the screening,” says My Catarina von Euler-Chelpin, an epidemiologist at the University of Copenhagen, who led the study published in the Journal of the National Cancer Institute. “However, it seems to have decreased as better and better screening technologies became available, which is hopeful news.”
The scientists studied the cancer histories of more than 58,000 Danish women, ages 50 to 69, following mammograms. Those who received a false alarm during screening in the 1990s had a 67 percent higher relative risk of being diagnosed with breast cancer later on, even six or more years after the scare.
False positives are caused by “suspicious patterns” that appear in the images of breast tissue, such as microcalcifications, skin thickening, or other abnormal cell growth. More than half of the women in the U.S. who get mammograms annually will have at least one false-positive result every 10 years. Previous studies found similar results with the short-term risk of being diagnosed with breast cancer following a false-positive, but von Euler-Chelpin and her colleagues’ study is the first to look at long-term risk.
But before you panic over a false-positive result, keep in mind that the study looked only at Danish women—and that may be good news for U.S. patients. Some experts have pointed out that the screening mammography in Denmark during the study differs from the recommendations of the American Cancer Society, which may make the study results less applicable to American women in 2012. Case in point: Many women in the Danish study did not receive four mammographic views (two of each breast)—something that is standard practice for every screening mammogram in the U.S. What’s more, the Danish study looked at screen-film mammography, which is used less frequently in the U.S. in favor of digital mammography.
More good news: Women who received false-positives after the year 2000 seem not to have an increased risk of developing breast cancer. Only 31 percent of them were diagnosed at a later date, a statistically insignificant difference from those who tested negative, according to the Danish scientists. Von Euler-Chelpin is unsure whether it is primarily due to better screening technologies, such as high-frequency ultrasound devices and bi-directional mammography, or too few cases from that period included in the study to accurately detect a trend.
“Mammography is just one tool in the shed,” Marisa Weiss, M.D., president of BreastCancer.org, told ABC News. “One thing this study shows is that additional diagnostic tools need to be used in a careful way. We need to give women the benefit of early detection while avoiding both false positives and false negatives.”
And headway is being made on that front. In February, the FDA approved another improvement to breast cancer detection technologies: 3D mammograms that use more radiation than traditional techniques, but are expected to be more accurate while detect cancers and reduce the number of false-positives.
Regardless of how applicable the study results are to U.S. women, the research “stresses the need for [women’s] adherence to regular screening,” according to the Danish scientists, and it may be up to doctors to push them to do it. Women who receive false-positive results during a mammogram are subject to high levels of stress and anxiety, according to von Euler-Chelpin, which may discourage them from undergoing regular screenings in the future.
“The hope is that better technologies will reduce the number of false-positives, which just may in turn lower the risk of women being diagnosed after receiving one,” says von Euler-Chelpin. “But in the meantime, it is crucial that women continue receiving mammograms according to their doctors' wishes, whether annually or biennially.”
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